The present invention relates to a method for granulation of relatively water-insoluble pharmaceutically active agents capable of forming a salt, to granular formulations thereof, and to pharmaceutical tablets made from such granular formulations. More specifically, the invention relates to drying an aqueous slurry of hydrolyzed cellulose or microcrystalline cellulose and one or more relatively water-insoluble pharmaceutically active agents which have at least partially been converted to more water-soluble salts to form granular formulations for use in the manufacture of pharmaceutical tablets and in filling capsules. The methods and compositions of this invention are particularly useful for relatively water-insoluble pharmaceutically active agents, such as salts of ibuprofen, which are not readily compressible into tablets after being dry blended with excipients. Compressible compositions containing salts of these relatively water-insoluble pharmaceutically active agents have greatly increased rates of dissolution.
Certain pharmaceutically active agents present challenges to dosage formulation. Ibuprofen, for example, is difficult to compress into tablets from a dry mix of excipients as heretofore practiced in the art. This lack of compressibility was overcome by a spray drying granulation technique described in U.S. Pat. No. 5,858,409. In the process described in this patent, hydrolyzed cellulose and the pharmaceutically active agent are mixed in a slurry, optionally with other excipients. This slurry is then spray dried to produce a granular composition which advantageously is comprised of granules, 90% of which are larger than 50 microns and smaller than about 500 microns. The median granule size is typically in the range of about 150 to 300 microns. Granules that are produced by this method are relatively porous, free flowing, substantially spherical, and readily compressible into pharmaceutical tablets having improved hardness, decreased friability, and excellent dissolution characteristics.
The present invention provides methods for granulating pharmaceutically active agents that have been at least partially converted into salts that are more water-soluble. These methods comprise mixing hydrolyzed cellulose, an aqueous solvent, and a relatively water-insoluble pharmaceutically active agent that has been at least partially converted into a more water-soluble salt form. In certain preferred embodiments, the methods of the invention comprise the steps of preparing a slurry that includes hydrolyzed cellulose, an aqueous solution of the salt form of a pharmaceutically active agent, and optionally, other excipients, and then drying the slurry.
The present invention also provides compositions comprising hydrolyzed cellulose in immixture with an aqueous solution that includes at least one relatively water-insoluble pharmaceutically active agent that has been at least partially converted into its more water-soluble salt form. Such compositions preferably are prepared either by adding a solution containing the salt form of the pharmaceutically active agent to a slurry of hydrolyzed cellulose in an aqueous solvent, or by adding the pharmaceutically active agent to the slurry and then at least partially converting it to its salt form in situ by reacting it with a suitable acid and/or base. Accordingly, one aspect of the present invention relates to compositions comprising hydrolyzed cellulose, water, at least one relatively water-insoluble pharmaceutically active agent, and an acid or base that is capable of reacting with said relatively water-insoluble pharmaceutically active agent and thereby converting it at least partially into its more water-soluble salt form.
In another aspect, the invention provides granular compositions that are produced by the drying process. These compositions contain about 1 percent to about 95 percent by weight of the relatively water-insoluble pharmaceutically active agent which has been at least partially converted into its more water-soluble salt and about 5 percent to about 99 percent by weight of hydrolyzed cellulose. In yet another aspect, the invention provides pharmaceutical tablets manufactured by compression of the granular composition of this invention which provide unexpectedly superior dissolution of the pharmaceutically active agent.
Dissolution of relatively insoluble pharmaceutically active agents which can be converted to a salt is significantly improved by conversion of at least a portion of the pharmaceutically active agent to its more water-soluble salt form in accordance with the present invention.